refactor: authenticate in main action if possible

Dockerfile

@@ -1,6 +1,10 @@
 FROM bycedric/ci-expo:2
 
 LABEL com.github.actions.name="Expo CLI (unofficial)"
-LABEL com.github.actions.description="Use any Expo command in your GitHub Actions workflow."
+LABEL com.github.actions.description="Use any Expo CLI command in your GitHub Actions workflow."
 LABEL com.github.actions.icon="terminal"
 LABEL com.github.actions.color="gray-dark"
+
+COPY entrypoint.sh LICENSE.md README.md /
+
+entrypoint ["/entrypoint.sh"]

entrypoint.sh

@@ -0,0 +1,11 @@
+#!/bin/sh -l
+
+set -e
+
+if [ -n "$EXPO_USERNAME" ] && [ -n "$EXPO_PASSWORD" ]; then
+	expo login --username $EXPO_USERNAME --password $EXPO_PASSWORD
+else
+	echo 'Skipping Expo login, username and/or password not defined...'
+fi
+
+sh -c "expo $*"